Weak Effects of Owned Outdoor Cat Density on Urban Bird Richness and Abundance

Abstract

Domestic cats (Felis catus) are ubiquitous predators of birds in urban areas. In addition to the lethal effect of predation, there can also be sublethal, negative effects of domestic cats on individual birds. These effects have led to the inference that reducing outdoor cat densities would benefit urban bird communities. Here we estimate the likely result of policies/programs designed to reduce densities of owned outdoor cats in urban areas, estimating relationships between bird richness/abundance and cat densities across 58 landscapes in Ottawa, Ontario, Canada. We estimate that we would most likely observe one additional bird species, and 0.003 additional individuals per species, if policies/programs reduced owned outdoor cat densities to zero in an average landscape in Ottawa (with 130.2 cats/km2). However, these effects of cat density on birds were uncertain, with 95% confidence intervals crossing zero. Our findings—in combination with those of previous studies—suggest a need for research to resolve the apparent disconnect between the strong, negative effects of cats on individual urban birds and the weak, uncertain effects of cats on bird populations. Although measures that reduce owned outdoor cat densities are justified based on the precautionary principle, evidence to date does not support prioritizing these measures over those addressing threats that have consistently strong effects on bird populations.

The impacts of free‐roaming cats cannot be generalized and their role in rodent management should not be overlooked

“…Common and introduced species were also the most common prey of cats in a study conducted in Australia (Franklin et al, 2021). Several studies have reported a lack of negative correlation between cats and bird densities (Perkins et al, 2021; Sims et al, 2008) and between cat activity and densities of native small and medium‐sized mammals (Lilith et al, 2010). Well‐fed cats also show reduced predation of wild animals (Cecchetti et al, 2021; Cove et al, 2018; Silva‐Rodríguez & Sieving, 2011).…”

Can we predict the predation pressure of owned domestic cats on all birds in the United States?

“…In continental ecosystems, particularly in North America, Eastern Europe and Australia, domestic cats have been estimated to consume billions of birds, mammals, amphibians and reptiles from hundreds of species annually, thus prompting calls for broad-scale reductions in cat populations (Blancher, 2013; Dauphine and Cooper, 2009; Doherty et al, 2017; Doherty et al, 2015; Loss et al, 2013; Woods et al, 2003, Woinarski et al, 2020). However, clear conclusions on the negative impacts of domestic cats on native populations are still lacking due to the limited number of studies investigating the ecological implications of domestic cat predation on wildlife (van Heezik et al, 2010; Kosicki, 2021; Marzluff et al, 2016; Perkins et al, 2021). Within the spectrum of domestic cat populations, owned domestic cats have garnered increasing interest regarding their impact on native fauna, especially in mainland regions (Woods et al, 2003; Brickner-Braun et al, 2007; Loss and Marra, 2017; Mori et al, 2019; Mella-Mendez et al, 2022).…”

Challenges and opportunities in human dimensions behind cat–wildlife conflict

“…Approximately 1.4−5.6 million feral cats subsist outside in Australia (Legge et al., 2017). In Ottawa, Canada, the average free‐ranging cat density is 130 cats/km 2 (Perkins et al., 2021), and in the United Kingdom, the median unowned cat density is 9 cats/km 2 in urban areas (McDonald & Skillings, 2021). These free‐ranging cats pose significant threats to wildlife in almost all ecosystem types worldwide through predation (Doherty et al., 2016), disease transmission (Espinaze et al., 2018), genetic introgression (Yu et al., 2021), and competition with indigenous carnivores (Henderson et al., 2021).…”